Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon.
A transistor is an element that is used frequently in semiconductor devices. There may be millions of transistors on a single integrated circuit (IC), for example. A common type of transistor used in semiconductor device fabrication is a metal oxide semiconductor field effect transistor (MOSFET), as an example. A transistor typically includes a gate dielectric disposed over a channel region in a substrate, and a gate electrode formed over the gate dielectric. A source region and a drain region are formed on either side of the channel region within the substrate.
In some transistor applications, it is desirable to introduce stress in the channel region of the transistor, in order to increase the mobility of semiconductor carriers such as electrons and holes. One method used to induce strain is embedded SiGe (eSiGe), which involves creating a recess in the source and drain regions of a MOS transistor, and growing a SiGe film within the recess in lieu of conventional silicon source and drain regions. The larger crystal lattice of the eSiGe creates stress in the channel region between the source and drain regions, enhancing carrier mobility. However, device shorts and junction leakage may result when a silicide is later formed on eSiGe source and drain regions.
Thus, what are needed in the art are improved methods of fabricating transistors and structures thereof.